Mounting arrangement for fixing a fan blade to a disk of a turbojet engine

ABSTRACT

A turbojet engine fan rotor including a rotor disk having a peripheral rim with a plurality of axially extending channels carrying a plurality of fan blades each having a blade root interengaging with the channels of the disk, and a mounting arrangement for securing the blades to the disk. The mounting arrangement includes an annular member having a plurality of radially extending teeth, a plurality of wedges each interposed between one of the blade roots and a corresponding one of the channels and including a radially extending boss provided at one end, and a plurality of radially extending protrusions from the disk. The plurality of teeth and the plurality of protrusions cooperate with one another to secure the annular member with the rotor disk.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a fan blade mounting arrangement for a turbojet engine rotor fan.

[0003] More specifically, the invention concerns a turbojet engine fan rotor comprising a plurality or detachable fan blades affixed to a disk rim defining a plurality of channels defined along the periphery thereof, each fan blade including a root mounted in a channel of the disk and dimensioned and configured in a corresponding manner. Each fan blade is secured in the channel with a wedge interposed between the blade root and an axial base surface of the channel. The mounting arrangement further includes an annular member resting against the disk having a plurality of radially extending teeth that cooperate with a plurality of radially extending protrusions of the disk to prevent axial displacement of the blades.

[0004] Hereinafter, in reference to a fan rotor of a turbojet engine, an upstream portion denotes a portion extending in the direction of the engine fore whereas a downstream portion denotes a portion extending in the direction of the rearward end of the engine. A radially inner portion denotes a zone near a central axis of rotation of the disk and a radially outer zone denotes a portion radially extended from the central axis of the disk.

[0005] 2. Summary of the Prior Art

[0006] One known mounting arrangement is disclosed in French patent document 2 681 374 which describes a mounting arrangement for turbojet engine fan blades. The mounting arrangement includes scalloped clamps situated upstream and downstream of the disk, and fitted with orifices adapted to affix two rings mounted on a front fairing and a compressor drum that cooperate with the ends of the blade roots in order to secure them in both an axial and radial fashion. Along the downstream portion of the roots, the fan blades are fitted with two spoilers that engage the radially inner and outer sides of a first ring, and further include two spoilers positioned along the upstream portion of the roots that engage the radially inner and outer sides of a second ring. This mounting arrangement requires complex machining of fan blades that are fitted with two spoilers at their ends, and also renders difficult and lengthy the replacement of a damaged blade due to the need to unscrew a plurality of affixation spindles which are positioned in the orifices of a scalloped flange which is difficult to access.

SUMMARY OF THE INVENTION

[0007] The objective of the present invention is to provide a mounting arrangement for a fan rotor such as described above wherein the blades are secured in a cascaded manner with respect to their axial displacements.

[0008] This objective is attained by wedges interposed between the blade root and the corresponding channel and further arranged at one of their ends with a boss that is interposed between the blade roots and the annular member. The disk includes along an upstream portion a plurality of radial protrusions that alternate with the channels. The annular member defines a plurality of radially extending teeth along a downstream portion that cooperate with a plurality of radially extending protrusions of the disk to prevent axial displacement of the blades. The radially inner portion of the annular member is fastened to a radially inner portion of the disk with a plurality of fasteners running parallel to the central axis of the disk.

[0009] Due to the mounting arrangement, the fan blades are secured in a significantly improved manner. The fan blades are mounted in the following manner: first, the fan blade rests on the wedge, then at least one radial tooth of the annular member cooperates partly with a disk protrusion to affix the fan blade in place, finally the plurality of fasteners securing the disk and annular member cooperate to lock the fan blade in place.

[0010] In case of an axial displacement of a blade, loads are absorbed simultaneously by the radial disk protrusions and the fasteners affixing the annular member on the disk. These fasteners therefore absorb only part of the loads. If the fasteners affixing the annular member on the disk include spindles, the present invention requires fewer spindles than used than in the prior art of the French patent document 2 681 374 A. Lastly, since the radial protrusions of the disk are without orifices to affix the annular member, they are able to withstand larger axial loads than the scalloped clamps of the French patent document 2 681 374 A.

[0011] Advantageously, the radial disk protrusions run radially outward and the radial teeth run radially inward. Another embodiment may include the radial protrusions running radially inward and the radial annular member teeth running radially outward.

[0012] Advantageously an axial clearance is subtended between the radial disk protrusions and the radial annular member teeth. This clearance permits dissipating part of the energy resulting from an axial displacement of the fan blade retained by the wedge.

[0013] In another embodiment of the invention, the fasteners affixing the annular member onto the disk comprise a plurality of spindles running parallel to the central axis of the disk.

[0014] The number of such spindles must be sufficient to retain the annular member against the disk when a fan blade is displaced axially. Advantageously, these spindles include a set of bolts and nuts capable of withstanding the axial and shearing loads.

[0015] The invention and its advantages are elucidated in the description below of illustrative and non-limiting embodiments, and in relation to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a cross-section of the mounting arrangement in accordance with the invention.

[0017]FIG. 2 is a section taken on line II-II in FIG. 1.

[0018]FIG. 3 is a partial isometric perspective view from downstream to upstream of the outer disk portion comprising a single wedge and showing the annular member in an unlocked relationship with the disk.

[0019]FIG. 4 is a view similar to FIG. 3 and depicts the annular member in a locked relationship with the disk.

[0020]FIG. 5 is a part sectional view of the mounting arrangement of the present invention.

[0021]FIG. 6 is a perspective view from upstream to downstream of the disk without the annular member.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022]FIGS. 1 and 2 show a fan rotor disk 10 having a central axis and a rim 12 arranged along a periphery thereof. The rim 12 includes a plurality of channels 14 axially extending along the central axis of the disk 10 at spaced apart angular intervals. Arrow F points in the direction from upstream to downstream portions and denotes the direction of the airflow.

[0023] The root 16 of a fan blade 18 is configured by being axially inserted into each channel 14. A wedge 20 is interposed between the blade root 16 and the base of the channel 14, thereby maintaining the blade root 16 secured against the walls of the corresponding channel 14.

[0024] Each wedge 20 is fitted with a boss 22 at one of its ends. Advantageously each boss 22 is configured at the upstream end of the wedge 20 between the upstream side of the blade root 16 and an annular member 24 which rests against the upstream side of the disk 10. The annular member 24 includes an inner wall of an annulus inwardly bounding the airflow duct through the fan.

[0025] At its upstream side and alternating with the channels 14, the disk 10 comprises a plurality of radial, outwardly extending protrusions 26. On its downstream side, the annular member 24 defines a plurality of inwardly extending radial teeth 28 that rest against the radial protrusions 26 of the disk 10.

[0026] In an alternate embodiment, the radial protrusions 26 of the disk 10 extend radially inward and the radial teeth 28 of the annular member 24 extend radially outward.

[0027]FIG. 3 shows the mounting arrangement in an unlocked position wherein the annular member 24 is not secured to the disk 10. In this embodiment, in order to secure the annular member 24 with the disk, the radial teeth 28 of the annular member 24 are inserted through notches 30 configured between the radial protrusions 26 of the disk 10 and situated above the bases of the channels 14.

[0028] Upon rotating the annular member 24 relative to the disk 10 about the central axis of rotation of the disk 10 and by an angle which is half the angle subtended between two consecutive channels, the radial teeth 28 move until opposite and downstream of the radial protrusions 26.

[0029]FIG. 4 shows the annular member 24 in the locked position. The width of the radial teeth 28 of the annular member 24 may be dimensioned greater than the radial protrusions 26 of the disk 10 in order that a fraction of each radial tooth 28 axially locks in position a portion of each fan blade 18.

[0030] The annular member 24 is maintained in position by a simple bolt/nut system.

[0031] The fasteners of the annular member 24 comprise locking elements consisting of small spindles fitted with bolts 44 and nuts 46. FIG. 5 shows a bracket 42 which is bolted down by bolts 44 and nuts 46 that are mounted onto the disk 10. The disk 10 remains unchanged in its radially inner portion and therefore assumes a simple geometry in its radially inward portion. The above-mentioned configuration also applies to the annular member 24.

[0032] The bolted bracket 42 simultaneously maintains the annular member 24 rotating relative to the disk 10 and secures it axially in place, entailing a corresponding number of spindles. FIG. 6 shows the disk 10 including along the radially inner portion a plurality of orifices that maintain the annular member 24 against the disk 10. Illustratively the affixation of the annular member 24 to the disk is implemented by a plurality of bolts 44 and nuts 46 in a manner to maintain the annular member 24 secured against the disk 10 even if there is loss of a blade.

[0033] The semi-joint axial latching of the mobile fan blades is carried out as follows: upon an axial displacement of a fan blade 18, the blade 18 is urged rest against the boss 22 of the wedge 20, whereby part of the radial teeth 28 of the annular member 24 prevents further movement of the fan blade 18. A clearance 48 is defined and subtended between the radial teeth 28 of the annular member 24 and the radial protrusions 26 of the disk for the purpose of dissipating some of the energy of the fan blade 18, whereupon the annular member 24 is able to deform before the radial teeth 28 thereby resting against the radial protrusions of the disk 10.

[0034]FIG. 5 shows bracket 42 and the set of fasteners 44, 46 that cooperate to lock the annular member 24 to the disk 10.

[0035] It will of course be appreciated that the invention is not confined to the particular embodiment described herein, but is intended to embrace all possible variations which might be made to it without departing from either the scope of spirit of the invention. 

We claim:
 1. A turbojet engine fan rotor including a rotor disk having a central axis and a peripheral rim with a plurality of axially extending channels at spaced apart angular intervals, a plurality of fan blades carried by said rim, each of said fan blades having a blade root interengaging with one of said channels of the rim of the disk and having surfaces configured and dimensioned corresponding to axially facing surfaces of said channels, and a mounting arrangement for securing said blades to said disk, said mounting arrangement comprising: an annular member having a plurality of teeth radially extending therefrom and spaced apart at regular angular intervals, said annular member having a radially inner portion fastened to a radially inner portion of said disk; a plurality of wedges each interposed between one of said blade roots and a corresponding one of said channels, each of said wedges having a radially extending boss provided at one end and axially interposed between said annular member and said blade roots; and said disk having a plurality of radially extending protrusions spaced apart at intervening angular intervals relative to said channels and disposed at angular positions of said plurality of teeth, said plurality of protrusions being arranged to overlap simultaneously with said plurality of teeth such that upon axial displacement of said blades, said plurality of teeth and said plurality of protrusions cooperate with one another to retain said annular member with said rotor disk.
 2. The rotor fan according to claim 1 wherein the plurality of teeth extend radially inwardly or outwardly according to an opposite direction of radial extension of said plurality of protrusions.
 3. The rotor fan according to claim 1 wherein each of said plurality of teeth subtend a clearance between a corresponding one of said plurality of protrusions, said clearance being parallel to said central axis of said disk.
 4. The rotor fan according to claim 1 wherein said radially inner portion of said annular member is fastened to said radially inner portion of said disk with a plurality of spindles running parallel to the central axis of said disk. 